1. Field of the Invention
The present invention relates to an electronic balance/scale (including both an electronic balance and an electronic scale) requiring warm-up operation for a prescribed duration before usage.
2. Description of the Prior Art
An electronic balance/scale performs warm-up operation for a prescribed duration before attaining a thermally stable state, in order to eliminate a thermal error of a load detection part resulting from temperature rise after power supply.
However, a conventional electronic balance/scale has no function of notifying that it is in warm-up operation to the user and the user must manage the duration from the start of power supply. Therefore, the electronic balance/scale may start measurement without performing sufficient warm-up operation, i.e., before the load detection part reaches a thermally stable state, to result in an incorrect measurement result due to influence by temperature drift. Or, the electronic balance/scale may excessively perform warm-up operation, to result in inferior working efficiency up to completion of measurement.
In consideration of the aforementioned circumstances, an object of the present invention is to provide an electronic balance/scale capable of performing measurement after proper warm-up operation.
The present invention provides an electronic balance/scale comprising a memory device storing data or a function related to the temperature characteristic of a load detection part, warm-up duration calculation means reading the data or the function stored in the memory device at the time of power supply for calculating a warm-up duration necessary for the load detection part to reach a thermally stable state in response to the state of the load detection part at the time of power supply on the basis of the data or the function, and notifying means notifying whether it is in warm-up operation or not on the basis of the warm-up duration calculated by the warm-up duration calculation means.
According to a first aspect of the present invention, the state of the load detection part employed by the warm-up duration calculation means for calculating the warm-up duration is a power shut down duration when power has been shut down. In order to calculate the power shut down duration, it comprises a clock device generating a signal indicating a time, a power shut down time storage processing means storing a power shut down time in the memory device on the basis of the signal from the clock device at the time of power shut down, and power shut down duration calculation means calculating the power shut down duration from the signal from the clock device and the power shut down time stored in the memory device at the time of power supply.
In this aspect, an example of the data or the function stored in the memory device is data indicating the relation between the power shut down duration and the warm-up duration, and the warm-up duration calculation means calculates the warm-up duration from the power shut down duration on the basis of the data.
Again, in this aspect, another example of the data or function stored in the memory device is the first data indicating the relation between the power shut down duration and the temperature of the load detection part and the second data indicating the relation between the temperature of the load detection part and the warm-up duration, and the warm-up duration calculation means calculates the temperature of the load detection part from the first data on the basis of the power shut down duration for calculating the warm-up duration from the second data on the basis of the calculated temperature.
Furthermore, in this aspect, still another example of the data or function stored in the memory device is a function deriving the warm-up duration while employing the power shut down duration as a variable, and the warm-up duration calculation means calculates the warm-up duration from the power shut down duration by an operation with the function.
According to a second aspect of the present invention, the state of the load detection part employed by the warm-up duration calculation means for calculating the warm-up duration is the temperature of the load detection part at the time of power supply, and it comprises a temperature sensor for detecting the temperature.
In the second aspect, the data or function stored in the memory device is data indicating the relation between the temperature of the load detection part at the time of power supply and the warm-up duration, and the warm-up duration calculation means calculates the warm-up duration from the temperature of the load detection part at the time of power supply on the basis of the data.
According to the present invention, the warm-up duration calculation means preferably sets the maximum necessary warm-up duration when energization comes first.
The notifying means can also serve as a display device for displaying a detection value of the load detection part. Alternatively, a device generating voice, a buzzer, or a notifying (warning) function of a CPU can be utilized as the notifying means.
Thus, the electronic balance/scale according to the present invention can measure weight after proper warm-up operation, thereby eliminating a measurement error resulting from temperature drift caused by a heat transfer characteristic specific to each of mechanical parts and electronic parts forming the electronic balance/scale.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.